1. Field of the Invention
The present invention relates to an apparatus for gas sensing by using fiber fabry-perot interferometer.
2. Background of the Invention
With development of science and industry, discharge of harmful gas has been increasing. Accordingly, studies on gas sensor to sense harmful materials are being activated also.
Traditional gas sensors are divided into tangential firing type gas sensor and semiconductor type gas sensor, which have several problems.
The tangential firing type gas sensor is a method to sense gas concentration by converting heat of reaction between combustible gas and oxygen to electrical signals, wherein the gas burns and generates heat of combustion on the surface of catalyst, so a filter able to reduce the thermal load from this should be provided. In addition, it treats the heat of reaction to electrical signals, so is significantly affected by neighbored magnetic field or electric field.
The semiconductor type gas sensor also uses alteration of the semiconductor's electrical conductivity by making the gas absorbed by loading heat to the semiconductor, so is also affected by heat, magnetic and electric field. Besides, long time is required for loading heat to 200˜300° C. and because it is sensitive to seasonal change of temperature and humidity, it may react to other gases (alcohols, solvent vapor, etc) than the gas to be sensed.
For gas sensing technology using optical manner, there are measuring devices using optical transmission and reflection and the optical manner gas sensors have merits that miniaturization and save of production cost of it is possible. Additionally, it facilitates insulation, is not interfered by electromagnetic power, and can be used for sensing pressure, humidity, chemicals, and biological molecules as remote sensing.